Essential divalent transition metals such as zinc, copper, and iron play important structural and catalytic roles in over 300 proteins. However, these and other transition metals also pose a potential threat to an organism. Left unchecked these metals can catalyze the generation of free radicals that damage all types of biological molecules. Transition metals must be kept in a physiological window. Diseases like Wilson's disease and Menke's disease demonstrate that either too much or too little metal can lead to pathologies of the liver, kidney, nervous system and connective tissues. Clearly metal homeostasis is an important aspect of cellular function. A major part of this control occurs at the level of transcription. One of the central players in this regulation is the metal response element binding protein (MTF-1). MTF-1 is a sequence specific DNA binding protein that perceives the metal status of a cell and activates genes accordingly. A good deal is known about MTF-1 itself, but very little is known about the protein co-factors that help MTF-1 efficiently activate transcription. We will use an RNAi based screen, in the Drosophila model system, to determine what protein co-factors are required for metal stimulated transcription. In addition we will characterize the physical and functional interactions between MTF-1 and these protein co-factors using a combination of cell based and in vitro assays. Finally we will identify the MTF-1 binding sites across the Drosophila genome to define the MTF-1 regulon that responds to metal stimuli. The long-term objective of our studies is to understand how a cell, in response to a diverse set of metals, differentially regulates the appropriate metal responsive genes to control metal homeostasis.